RINFEC · The Roots of Infection

Plant roots and soil microbes have been associated since the emergence of plants on land. Nevertheless the mechanisms that have coevolved to control these commensal and mutualistic associations are currently unknown. RINFEC will identify both plant and bacterial genes involved in root colonization by commensal and mutualistic bacteria with an approach that would be transformative in the field. The ambitious challenge is to identify and functionally characterize the central genes controlling root cells competence for infection. RINFEC´s central hypothesis is that key components of ancient pathways for bacterial colonization of the root surface (rhizosphere) and root interior (endosphere) were adapted during evolution of mechanism(s) controlling colonization of legume roots by symbiotic rhizobia. RINFEC will uncover the genetics and biochemistry of these shared mechanisms by characterizing a novel, unexplored intercellular infection mode observed for certain rhizobia that act as endophytes in non-legume plants and are able to infect the model legume Lotus japonicus. The unique biological feature exploited in RINFEC is the capacity of Lotus to support either intercellular entry (conserved mode) or legume specific infection thread entry, dependent on the rhizobia encountered. This allows comparative investigations of these two infection modes in simple binary interactions with the same host. Given the exceptional ability of different rhizobia for intercellular endophytic colonization of non-legume roots this provides an unprecedented platform to identify mechanisms by which plants selectively enable a subset of bacteria to infect roots. RINFEC will build on my considerable expertise with Lotus and pioneers novel plant and bacterial genetic methods, cell-layer transcriptomics, phospho-proteomics and advanced biochemistry to break new ground in understanding infection and soil microbe influences on plant performance under environmental stress conditions.